Field of the Invention
The present invention relates to a shift control method of an automatic transmission and a shift control apparatus using the aforementioned method.
Description of Related Art
An automatic transmission changes gear ratios according to a running state of a vehicle in order to perform shifting to a target gear stage.
In a case in which the shifting to the target gear stage is performed, an automatic transmission has an off-going element that changes from an engaged state to a release state and an on-coming element that changes from a released state to an engaged state. Releasing an off-going element and engaging an on-coming element is realized by controlling hydraulic pressure supplied to respective elements. In addition, the control of the hydraulic pressure supplied to the off-going and on-coming elements is performed by operating a control duty and controlling the solenoid valve according to the control duty.
In general, in a case in which shifting is performed according to the conventional shift control method, slips of an off-going element and an on-coming element are used in order to synchronize a speed of an input shaft and a speed of an output shaft of an automatic transmission. However, in the method in which the speed of the input shaft and the speed of the output shaft are passively synchronized by the slips, shifting time is lengthened and shift quality may be deteriorated according to running conditions (e.g., a slope of a road and a vehicle load). To solve this problem, calibration maps that correspond to each running condition may be prepared previously, but it is impossible to infinitely increase the number of calibration maps. In addition, it is difficult to expect good shift quality in a running condition that is not considered. Further, since a torque converter is not generally used in a hybrid vehicle in order to improve fuel efficiency, bad shift quality may adversely affect vehicle drivability.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.